In the United States, approximately 400,000 people have end-stage renal disease requiring chronic hemodialysis. Permanent vascular access sites for performing hemodialysis may be formed by creating an arteriovenous (AV) anastomosis whereby a vein is attached to an artery to form a high-flow shunt or fistula. A vein may be directly attached to an artery, but it may take 6 to 8 weeks before the venous section of the fistula has sufficiently matured to provide adequate blood flow for use with hemodialysis. Moreover, a direct anastomosis may not be feasible in all patients due to anatomical considerations. Other patients may require the use of artificial graft material to provide an access site between the arterial and venous vascular systems. Although many materials that have been used to create prosthetic grafts for arterial replacement have also been tried for dialysis access, expanded polytetrafluoroethylene (ePTFE) is the preferred material. The reasons for this include its ease of needle puncture and particularly low complication rates (pseudo-aneurysm, infection, and thrombosis). However, AV grafts still require time for the graft material to mature prior to use, so that a temporary access device, such as a Quinton catheter, must be inserted into a patient for hemodialysis access until the AV graft has matured. The use of temporary catheter access exposes the patient to additional risk of bleeding and infection, as well as discomfort. Also, patency rates of ePTFE access grafts are still not satisfactory, as the overall graft failure rate remains high. Sixty percent of these grafts fail yearly, usually due to stenosis at the venous end. (See Besarab, A & Samararpungavan D., “Measuring the Adequacy of Hemodialysis Access”. Curr Opin Nephrol Hypertens 5(6) 527-531, 1996, Raju, S. “PTFE Grafts for Hemodialysis Access”. Ann Surg 206(5), 666-673, November 1987, Koo Seen Lin, L C & Burnapp, L. “Contemporary Vascular Access Surgery for Chronic Hemodialysis”. J R Coll Surg 41, 164-169, 1996, and Kumpe, D A & Cohen, M A H “Angioplasty/Thrombolytic Treatment of Failing and Failed Hemodialysis Access Sites: Comparison with Surgical Treatment”. Prog Cardiovasc Dis 34(4), 263-278, 1992, all herein incorporated by reference in their entirety). These failure rates are further increased in higher-risk patients, such as diabetics. These access failures result in disruption in the routine dialysis schedule and create hospital costs of over $2 billion per year. (See Sharafuddin, M J A, Kadir, S., et al. “Percutaneous Balloon-assisted aspiration thrombectomy of clotted Hemodialysis access Grafts”. J Vasc Intery Radiol 7(2) 177-183, 1996, herein incorporated by reference in its entirety).